Semiconductor transducer or actuator utilizing corrugated supports

ABSTRACT

A semiconductor transducer or acutator is disclosed. The transducer and actuator each include a deflecting member with corrugations producing increased vertical travel which is a linear function of applied force. An accurate and easily controlled method that is insensitive to front-to-back alignment is also disclosed for forming uniform corrugations of precise thickness; independent of the thickness of the deflecting member. The cross-sectional shape of the corrugations is not limited by the etching technique, so that any configuation thereof is enabled.

This is a division of application Ser. No. 07/335,185, filed Apr. 7,1989, U.S. Pat. No. 5,064,165.

FIELD OF THE INVENTION

This invention relates to semiconductor transducers and actuators havinga deflecting member and more particularly to a transducer and anactuator utilizing corrugations in the supports of the deflectingmember.

BACKGROUND OF THE INVENTION

Typical diaphragm-type transducers and actuators employ a thin diaphragmof a circular, square or rectangular plan configuration. When thisdiaphragm is subjected to a force, the deflection of the diaphragmreflects the magnitude of this force. It is well known that thedeflection of such a diaphragm is linear with applied force or pressureso long as the deflection is a small fraction of the thickness of thediaphragm. As the force or pressure is increased beyond this point, thedeflection becomes a non-linear function of the applied force orpressure due to the stretching of the diaphragm. In many applicationsthis non-linear travel limits the useful range of the device. Flatdeflecting beams that stretch when subjected to an applied force orpressure have a similar problem. These diaphragms or beams are typicallyused as the movable element in pressure transducers and actuators, butcan also be used in accelerometers, force transducers, or displacementtransducers.

As diaphragms are made thinner, the above-mentioned non-lineardeflection characteristic of the diaphragm is exacerbated. Hence,typically, to provide a low pressure transducer or actuator having asatisfactory linear operating range requires that the diaphragm belarger. This is unacceptable for many applications where there are sizeconstraints. For example, it is important that pressure transducersformed using semiconductor materials be as small as possible.

Another problem arises when a flat diaphragm which is clamped at itsedges, is subjected to a differential pressure. The central region ofthe diaphragm is bent into a curved shape rather than moving up and downin a piston-like manner. If, as typically is the case, the measurementof the deflection of the diaphragm is done by capacitor plates attachedwith one plate on the diaphragm and a second plate on a surface oppositethe diaphragm, the measurement will be complicated because the shape ofthe diaphragm plate changes with applied force or pressure. Further, itis known that a relatively large movement of the diaphragm isadvantageous when measuring the deflection by capacitive means since thechange in capacitance is related to the reciprocal of the gap betweenthe plates of the capacitor. For very sensitive flat diaphragms, thelinear deflection is only a small fraction of the thickness of thediaphragm. This requires that the capacitor plates be positioned with agap having a width which is also a fraction of the diaphragm thickness.Achieving such a small capacitor gap can greatly complicate the assemblyof such a structure. If the small gap cannot be realized, the change incapacitance for a given applied force or pressure will be severelylimited.

It is known that corrugated diaphragms provide certain advantages overflat diaphragms when utilized in a pressure transducer. For purposes ofthis specification, what is meant by a corrugation is a structure havingone or more grooves separated by a thin section that allows compliantmovement. For corrugated diaphragms, the compliance in the groovessubstitutes for the stretching that would occur in flat diaphragms. Theprimary advantage of a corrugated diaphragm is that there is a morelinear vertical travel per unit of applied force. For example, it istaught in Flat and Corrugated Diaphragm Design Hanbook by Marco DiGiovanni (published by Marcel Dekker, Inc.) that a diaphragm of similarsensitivity and diameter will have more linear range and stiffness if ithas a corrugated support rather than a flat support. Hence, corrugateddiaphragms are utilized advatageously to increase the range of lineartravel of the transducer as a function of applied force.

Therefore, in order to alleviate diaphragm non-linearity due tostretching, metallic structures have been used wherein the diaphragm isformed with corrugations. Corrugated diaphragms of this type have beenfound to exhibit a larger range of linear deflection to appliedpressure, thereby minimizing the stretching effect. Typically, suchdiaphragms are used in conjunction with a push rod and beam to form arelatively complex pressure responsive mechanism. A problem with suchdiaphragms is that they must be machined or formed from suitable metalsand are difficult to manufacture. Furthermore, the strain sensorslocated thereon need to be separately positioned and mounted on thesecorrugated structures, resulting in additional problems which affectperformance within the linear range.

The above-described manufacturing and performance problems of corrugateddiaphragm sensors are minimized if semiconductors processing techniquescan be used. U.S. Pat. No. 4,467,656 to Mallon, et al. teaches that aconvoluted diaphragm can be formed in silicon. Piezoresistive devicesare diffused into the convolutions using integrated circuit methods. Theresult is a pressure transducer that can be fabricated from a siliconsubstrate by etching concentric recesses or corrugations on both sidesof the substrate. The corrugations are surrounded by a rigid peripheralarea.

U.S. Pat. application No. 4,236,137 to Kurtz et al. discloses a pressuretransducer having a semiconductor diaphragm with a central boss area oftrapezoidal cross-section surrounded by a continuous groove. A pluralityof piezoresistive sensors are formed on the diaphragm with a firstsensor adjacent to the outer edge of the groove and a second sensorparallel to the first sensor and being adjacent to the inner edge of thegroove. The groove is operative as a stress concentrating area for thesensors. It is known, however, that a single groove does notsubstantially improve the linearity of diaphragm travel over that of aflat diaphragm structure. Therefore, although this structure is usefulin some applications for edge stress measurement, it would not beeffective in many applications for the same reasons that flat diaphragmsare not effective.

In many transducer applications, such as in accelerometers, it isnecessary to measure the force perpendicular to the plane of thediaphragm. The accelerometer typically has a centrally positioneddeflecting member that deflects in response to an applied force, thevertical travel of the deflecting member being a measure of the appliedforce.

A key problem with previous transducers utilizing corrugations is thatthere are stress points located within the corrugations that canadversely affect the operation of the transducer. It is known thatcorrugations formed by anisotropic etch techniques are trapezoidal inshape and that the trapezoidal corrugations will have stressconcentrated in the corners of the corrugations. Hence, if an excessiveamount of pressure is applied to the transducer, the corrugations maycrack at those corners, rendering the transducer inoperative.

Mallon, et al., notes that isotropic etching could be used to provide arounded configuration, but does not disclose how to achieve such astructure. In fact, Mallon, et al. teaches that the anisotropic etch ispreferred and the stress problem caused by these types of corrugationsis not addressed. It is well known that conventional isotropic etchtechniques are difficult to control and the corrugations producesutilizing isotropic etch techniques may not be uniform, thereby causingstress to be still concentrated therewithin.

It is also known that producing corrugations utilizing known processingmethods can be very difficult when thin diaphragms are formed for lowpressure measurements. In a typical process, each side of a siliconmaterial is masked utilizing typical photolithography techniques andthen each side is etched into the desired pattern. This processtypically requires precision alignment instruments to ensure that frontand back surfaces match. If the surfaces do not match, then theresultant corrugations will not be properly formed, which seriouslyaffects the performance of the transducers. In particular, when thinstructures are formed (on the order of 0.5 μm to 10 μm), thenmisalignment becomes very significant, often to the point of renderingthe transducer inoperative.

A final related problem with corrugated diaphragm structures is that thedepth of the corrugations and the thickness of the deflecting membereach affect the deflection charcteristics of the structure. When thecorrugated diaphragm structure is produced via the above procedure, thenthe deflecting member must be masked with the corrugations. In theresultant structure the corrugations can only be the same thickness asthe deflecting member. Therefore, since the corrugation and deflectingmember thicknesses are related, the dimensions of the transducer formedby these processes are limited by that dependence.

Accordingly, it is a principal object of the present invention toprovide a semiconductor transducer or a semiconductor actuator that hasincreased linearity of travel per unit of applied force or pressure.

It is another object of the present invention to provide a method forproducing a corrugated structure to be utilized with a transducer oractuator that overcomes some of the fabrication problems associated withknown semiconductor processing techniques.

It is yet another object of the present invention to provide asemiconductor transducer or a semiconductor actuator which overcomessome of the problems associated with previous diaphragm transducer oractuator assemblies.

It is a further object of the present invention to enable corrugationformation to be less dependent on front-to-back alignment of thesemiconductor starting material.

It is still a further object of the present invention to provide atransducer or an actuator which maximizes the deflection for a givenapplied force or pressure.

It is yet a further object of the present invention to provide animproved method for forming a semiconductor transducer or asemiconductor actuator which allows the predetermined thickness of thedeflecting member to be independent of the predetermined thickness ofthe corrugations.

SUMMARY OF THE INVENTION

In a first aspect of the present invention, an improved semiconductortransducer is disclosed. The transducer comprises a semiconductor layerhaving a centrally positioned, rigid deflecting member, a support memberand a plurality of corrugations coupled between the deflecting memberand a support member. The transducer also includes means for sensing thedeflection of said deflecting member and for developing an electricalsignal as a function of the sensed deflection of said deflecting member.The corrugations provide for increased linear vertical travel of thedeflecting member per unit of applied force than for similar flatsemiconductor transducers.

In a second aspect of the present invention, an improved semiconductoractuator is disclosed. The actuator comprises a semiconductor layerhaving a centrally positioned, rigid deflecting member, a support memberand a plurality of corrugations coupled between the deflecting memberand the support member. The actuator also includes means for applying aforce to the deflecting member and for utilizing that deflection inconjunction with a separate structure, device, or physical medium. Thecorrugations provide for increased vertical travel of the deflectingmember compared to flat diaphragms of similar size, thus allowing forgreater effect on the affected structure, device, or medium.

In another apsect of the present invention, a method for formingcorrugations in a semiconductor material is disclosed. The methodcomprises the steps of masking a first surface on said semiconductormaterial in accordance with a predetermined pattern, etching saidsurface in accordance with the pattern to provide a predeterminedprofile on the surface, removing the mask from the surface, providing anetch stop on the first surface in accordance with the predeterminedprofile and etching a surface opposite the first surface to the etchstop to form the corrugations.

By utilizing this procedure, a semiconductor transducer or actuator isproduced that is less susceptible to stress concentrations than previouscorrugated structures. In addition, due to the etch stop procedure,there is no need for alignment of the structure to provide forfront-to-back orientation. This method also allows for the deflectingmember thickness to be independent of the corrugation thickness.Finally, the method of the present invention is substantially easier tocontrol than previous methods and has increased utility in manufacturingprocesses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a prior art semiconductor transducer.

FIG. 2 is a cross-sectional side view of the prior art semiconductortransducer of FIG. 1.

FIG. 3 is a top plan view of a diaphragm semiconductor transduceraccording to the present invention.

FIG. 4 is a cross-sectional side view of a diaphragm semiconductortransducer according to the present invention.

FIG. 5A-D is a simplified diagrammatic view of the method of producing asemiconductor transducer or actuator according to the present invention.

FIG. 6 is a cross-sectional side view of a beam semiconductor transducerin accordance with the present invention.

FIG. 7 is a cross-sectional side view of a diaphragm semiconductoractuator in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It is known that flat (meaning non-corrugated) semiconductor diaphragmshave displacements that are nonlinear functions of the applied force orpressure. Hence, flat diaphragms must be down-rated or their overallrange of linear displacement must be reduced to maintain a linearresponse at low pressures. Therefore, flat diaphragms are generallyunsuitable for low pressure measurements.

As mentioned, corrugated diaphragm structures have been utilized insemiconductor device for measuring edge stress. FIGS. 1 and 2 exemplifythis type of diaphragm structure.

FIG. 1 is a top plan view of a prior art pressure trnasducer 10employing a corrugated diaphragm 11. Diaphragm 11 is shown relativelysquare, but other configurations can be employed. Diaphragm 11 can befabricated from, for example, single-crystal silicon. The surface ofdiaphragm 11 contains a series of concentric grooves or corrugations 14of increasing size which form squares in the plan view.

FIG. 2 is a cross-sectional side view of pressure transducer 10 of FIG.1 through section 2--2. Pressure transducer 10 may be mounted on asupport member 17 which is bonded about the periphery of the diaphragm11 by means of glass bonding or the like. Support member 17 may befabricated from silicon, metal or glass and has an aperture 19 whichserves as a pressure port.

As can be seen, corrugations 14 of diaphragm 11 are trapezoidal incross-section, forming crests and valleys shown generally at 18 and 20.The central area of diaphragm 11, designated generally at 16, iscorrugated and has a given thickness. Each corrugation 14 is formed byan anisotropic etch which produces the sloping sidewalls 22.

Pressure transducer 10 of FIGS. 1 and 2 is utilized to measure edgestress at its outer edge. Typically, piezoresistive sensors are placedon an edge of transducer 10 providing a measure of the level of appliedforce by producing an electrical signal in response to a change instress. The linear travel of corrugations 14 is greater than that offlat diaphragms, but pressure transducer 10 is not suitable for certainapplications.

A problem with the above-mentioned prior art structure is that centerdeflections are measured indirectly with piezoresistive elements at theperiphery of the diaphragm. Piezoresistive sensing is not optimum formany applications because (1) there are large changes in sensitivitywith temperature, (2) there are errors from leakage currents from theresistive elements, and (3) typical changes in stress produce smallchanges in resistance which must be accurately detected. Hence, for manyapplications, a structure which does not require piezoresistive elementswould be desirable.

Another problem with known corrugated pressure transducers is thatprecise front-to-back groove alignment is required and this is difficultto achieve. In a typical process, photolithographic masks are depositedon both sides of the starting material. Then both sides are etched untilthe structure is formed. At this step, it is crucial that the front andback side masks match to ensure that the corrugation formed has theproper configuration. As the corrugation thickness decreases, thisalignment of the front and back of the diaphragm becomes increasinglyimportant. In low pressure transducers, the thickness of thecorrugations is usually between 0.3 μm and 20 μm.

At these thicknessess, even minor misalignment of the front and backsides of the mask would render the transducer inoperative. Hence,considerable time and expense is required in aligning the material whichsignificantly increases manufacturing costs, which in turn may prohibitcommercial viability.

In addition, as mentioned, in prior art fabrication, the thicknesses ofthe deflecting member and the corrugations are dependent upon eachother. This inhibits the use of materials and fabrication processes.

Another problem with prior art corrugated pressure transducers is thatthe interior corners of the anisotropically etched grooves etch awayvery quickly. This is described in Bean, K.E., "Anisotropic Etching ofSilicon", IEEE Transactions on Electron Devices, Vol. ED-25, No. 10;October 1978, pp. 1185-1193. This means that the masks used to producethe etched grooves must include corner compensation means which aredifficult to control and which greatly complicate the fabricationprocess. For instance, if the corner compensation is only very slightlylarger than the optimum, the diaphragm will be substantially thicker inthe corner regions. This will increase the stiffness of the diaphragmsand concentrate stress in the structure. If the compensation is veryslightly smaller than optimum, the diaphragm will etch through in thecorners resulting in a hole in the diaphragm and thereby rendering thewhole structure inoperative.

Prior art fabrication processes of corrugated pressure transducers alsoare not able to precisely control diaphragm thicknesses. For example,the thickness in the top 18 of the trapezoid of diaphragm 11 (FIG. 2) isset by the etch rate of the etchant, the time in the etchant, and thethickness of the starting wafer. Prior art processes are adequate forthicknesses to approximately 5% of the depth of the etched groove. It isdesirable to provide diaphragms which are as thin as 0.5 μm and thislimits the thickness of the starting material to approximately 10 μm.Wafers of this thickness cannot be practically processed usingconventional methods.

Although corrugations have been discussed primarily in the context ofutilization in a diaphragm in a pressure transducer, it is understoodthat there are other microminiature mechanical devices formed insemiconductor materials in which corrugations would also have utility.For example, U.S. Pat. No. 4,543,457 assigned to Transensory Devices,Inc., describes a beam utilized in a semiconductor apparatus which bendsin response to pressure.

FIG. 3 is a top plan view of a first embodiment of a transducer 30 inaccordance with the present invention. Transducer 30 has a substantiallysquare configuration, but rectangular, circular or other configurationssuch as arcs, spirals, serpentines, and radials are also within thescope of the present invention. Typically, transducer 30 is constructedfrom a silicon material. However, one of ordinary skill in the art willrecognized that there are a variety of other types of materials thatcould be used. For example, in the present invention, the diaphragm oftransducer 30 can be composed of sputtered or evaporated metal, platedmetal, vapor-deposited dielectrics such as silicon dioxide or siliconnitride, polymers such as polyimide or Parylene™ or other materialsknown in the industry. Various materials are useful in differentapplications where their properties can be advantageously used to impartdesirable characteristics to the device.

Transducer 30 includes a layer 32 of semiconductor material having acentrally positioned, rigid deflecting member 38 surrounded by aplurality of corrugations 34, and a support member 36 coupled to theouter periphery of corrugations 34. In this embodiment layer 32 formsthe diaphragm for transducer 30.

FIG. 4 is a cross-sectional side view of FIG. 3 through 4--4. As seen inFIG. 4, the transducer 30 according to the present invention ispreferably formed from a semiconductor layer 32. Semiconductor layer 32includes a support member 36 and a diaphragm 35 which in turn comprisesa deflecting member 38 and the corrugations 34 on sides of deflectingmember 38. The top surface 40 of deflecting member 38 is preferably onthe same plane as the top surface 42 of support member 36. The bottomsurface 41 of deflecting member 38 is preferably parallel to surface 40.A superstrate 44 having a well 46 formed on a first surface thereof ispreferably bonded to surface 42 of support member 36. Sensing means forsensing travel of deflected member 38 includes a sensing element 50disposed on the first surface of superstrate 44 in well 46 oppositedeflecting member 38, and a sensing element 48 disposed on deflectingmember 38 oppposite sensing element 50. Sensing means 48, 50 can be anymeans that senses the movement of deflecting member 38 and produces anelectrical signal in response to that movement. In one preferredembodiment, sensing means 48, 50 comprises two capacitive plates. It isunderstood, however, that sensing means 48, 50 could be any mechanical,optical, or like means which accomplishes the stated purpose. Anaperture 37 through superstrate 44 communicates with well 46 to serve asa pressure port.

Corrugations 34 allow deflecting member 38 to move up and down in apiston-like manner for a greater vertical distance than enabled withnon-corrugated diaphragms. Thus, the linear relationship between thevertical travel and the applied force holds over a greater distance thanthat for flat diaphragms. Furthermore, corrugations 34 significantlyincrease the overall linearity of transducer 30 compared to prior arttransducers. For this reason, pressure transducer 30 can be utilizedmore effectively with capacitive sensors than previously knownsemiconductor transducers.

Another advantage of the present invention is that corrugations 34 canbe formed to have a wide variety of different paths along the planedeferred by surface 40, 42. In transducer 10, as seen in FIG. 1, thepaths are generally square with slightly rounded corners, but the pathscould be any of a wide variety of possible paths such as circular,spiral, serpentine, radial, or a series of arcs. Such paths have beenused in conventional prior art metal diaphragms, but are not possible tomake using prior art fabrication methods for semiconductor corrugateddiaphragms.

Still another advantage of the present invention is that thecorrugations are preferrably curved in cross-section to minimize thestress in the corrugations. The previously mentioned references,particularly Mallon, et al., teach as a preferred method anisotropicallyetching the silicon material, thereby producing corrugations having atrapezoidal corss-section. Mallon et al. states only that it is possibleto isotropically etch a curved pattern, but it is well known thattypical isotropic etch techniques are difficult to control and that thecorrugations formed thereby may not be uniform in thickness, producing asource of stress which may result in operability.

As also mentioned, in previous methods a crystal of silicon material ismasked utilizing well known photolithographic techniques. Then both thefront and back sides of the material are anisotropically etched to formthe desired corrugated surface. This type of etch creates the sharpcorners shown in the corrugations of the transducer of FIG. 2.

If, however, the material is etched utilizing isotropic techniques, thenit is harder to control the width and the depth of the corrugations.This leads to a corresponding difficulty in ensuring the uniformity ofthe corrugations. If the corrugations are not uniform, then there is astrong possibility that stress will be concentrated in certain points,similar to the corrugations formed by anisotropic etchants.

As mentioned, prior art etch techniques also have the problem of beingdifficult to provide accurate front-to-back alignment. Since the etchingtakes place on both sides of the material, it is important that eachside be aligned with the other. This is difficult because it isimpossible to "see" the etch on the opposite side. This is a significantproblem when low pressure transducers are formed from semiconductormaterial. As mentioned, the diaphragms associated with these transducersare very thin (on the order of 0.3 μm to 20 μm). The etching processmust then be very precise to produce uniform corrugations.

Finally, with prior art processes, the thickness of the support memberand deflecting members were directtly related to the thickness of thecorrugations. As mentioned, this limited the manufacturability of thetransducer.

The present invention provides a process for forming corrugated pressuretransducers and actuators which overcome the above-mentioned problems.FIGS. 5A through 5D are simplified cross-sectional views of a processaccording to the present invention.

A wafer or layer of silicon 58 comprises starting material to form acorrugated deflecting member. First, a top surface 60 of layer 58 ismasked by depositing either an oxide or a nitride layer 70. A secondsurface 62 of layer 58 is masked either at this point or later in thesame fashion, as described below. Thereafter, as is seen in FIG. 5A, aportion of the layer 70 is removed in the areas where the corrugationsare to be etched (shown generally at 64). Then top surface 60 of thesilicon material is etched using a standard silicon etching gas, such assulfur hexafluoride. Typically, this type of etching is done by aconventioanl plasma etch method. Alternatively wet chemical etching canbe used. For example, an isotropic etch can be achieved using liquidmixtures of, for example, 90% nitric acid and 10% hydrofluoric acid.

Depending upon the gas pressure and the type of plasma etcher used, theetch profiles can be varied from nearly vertical sidewalls to anisotropic type profile 61, as shown in FIG. 5B. The depth of etchedprofile 61 is controlled by varying the etching time, the RF power andgas pressure in accordance with standard processing techniques. When anisotropic etch is used, the opening in the etch mask compensates for theamount of undercutting inherent in the isotropic etch process.

Referring to FIG. 5C, etch mask 70 is then removed from top surface 60.Thereafter, an etch stop 66 is diffused into top surface 60. Etch stop66 is typically provided by doping top surface 60 with an impurity. Onesuch etch stop is a heavily doped boron region. The thickness of thedoped layer can be controlled by using standard predeposition andthermal driving techniques known in the integrated circuit industry.Typically, the doped layers can be made to a depth between 0.3 μm and 20μm with great accuracy.

A mask is created in the layer 70 formed on the bottom surface 62 inaccordance with a second predetermined pattern. This mask pattern isdesigned to form a central deflecting member 76, as seen in FIG. 5D, anda support member 78. Bottom surface 62 is then etched to remove thesilicon material up to etch stop 66. In so doing, corrugation 68 arecreated which do not exhibit the previously described deficiencies ofprior art corrugations. In this embodiment of the present invention, theetch taken from the bottom surface 62 is an anistropic etch whichproceeds until etch stop layer 66 is the only material remaining in theetched region.

A second embodiment of the method of the present invention includessubstituting the deposition of a thin film material in place of theinclusion of etch stop 66. This thin film material may be a sputtered orevaporated metal film, a plated metal film, a vapor deposited dielectricfilm such as silicon dioxide or silicon nitride, a polymer coating suchas polyimide or Parylene^(TM), or other materials known in the art.Under appropriate deposition conditions, these films are generallyconformal, following the contours of etched grooves 61 to form a layerthat is substantially identical to layer 66. The thin film substitutingfor etch stop 66 can be chosen so as to be unaffected by the etch usedto pattern bottom surface 62, and thus corrugations will be producedwhich are substantially the same as corrugations 68 shown in FIG. 5D.Thus, the materials used to form corrugations 68 are not limited to thatof the semiconductor substrate 58. Such other materials are useful invarious applications where their different material properties can beadvantageously used to impart desirable characteristics to thedeflection of central deflecting member 76.

The processes of the present invention have several advantages overprior art processes. First, since etch stop 66 is provided on a topsurface of the wafer, the corrugations can be of any configuration. Forexample, as shown in FIG. 5D, corrugations 68 are rounded, therebyobviating much of the stress inherent in prior art trapezoidalcorrugations.

Second, etch stop 66 also obviates the front-to-back alignment problem.Etch stop 66 controls not only the desired depth of the corrugations,but also the contour of the region. As mentioned before, thecorrugations formed by prior art methods require precise alignmentbetween the front and back. With the method of the present invention,there is no alignment problem. This allows efficient, cost-effectivefabrication of corrugations using semiconductor or other materials ofvarious paths such as spirals, serpentines, radials, and the like.

Third, in the method of the present invention, the thickness of thecorrugations is independent of the thickness of the deflecting member.Thus, the thickness of either member is not limited by the other.

Fourth, the use of etch stop 66 produces a diaphragm or like member ofsubstantially constant thickness, regardless of the shape of thecountour. This reduces the concentration of stress in the diaphragm orlike member due to thickness variations and thus increases the traveldistance of the diaphragm.

Fifth, it will be recognized that the process of patterning, and/oretching, and/or the formation of etch stop regions on surface 60 can berepeated to form more complicated structures. It is well known in thefield of corrugated metal diaphragms that deepr edge beads, i.e. outsidesupports, provide improved diaphragm response in some situations. Thiscan be provided within the scope of the present invention by a pair ofmasking and etching steps before the inclusion of etch stop 66.Similarly, it is often advantageous to provide thicker or thinnersupport regions in or around corrugations 68. This can be providedwithin the scope of the present invention by providing a plurality ofetch stops, each formed by a separate masking and deposition step. Sincethese etch stop regions are defined by the location of masking layerssimilar to layer 70 on surface 60 and not by the possible crystallinenature of layer 58, these support regions can be provided in a varietyof configurations, including rectangular, circular, annular, spiral,radial, and serpentine. Thus, for example, central deflecting member 76can be provided by the inclusion of a deeper etch stop region interiorto corrugations 68. Similarly, thicker etch stop regions betweencorrugations 68 and support member 78 can be provided to control theconcentration of stress between these structures.

Accordingly, for the above-mentioned reasons, the present invention hassignificant advantages over prior art transducers, actuators, andmethods of producing same.

Although this invention has been described primarily with regard to adiaphragm structure, it is understood that the advantages of increasingthe vertical travel and range of linearity provided by corrugations canbe applied to other structures. FIG. 6 is a cross-sectional side view ofa transducer 80 that utilizes a bending member 82.

In FIG. 6, semiconductor transducer 80 includes a substrate 84 which iscoupled to a bending member 82. Substrate 84 includes a bottom section81 and an upwardly extending section 85 coupled to one end of bottomsection 81. Bending member 82 comprises a beam member 83, a supportmember 86 and a plurality of corrugations 88 coupled therebetween.Substrate 84 has a well 90 disposed in bottom section 81. Beam member 83is suspended in a longitudinal direction over well 90. Disposed in well90 on a first surface of substrate 84 is well sensing element 92.Attached to a first surface of beam member 83 and opposite sensingelement 92 is beam sensing element 93.

Beam member 83, because of corrugations 88, is capable of increasedtravel per unit of applied force compared with prior art flat beams.Hence, transducer 80 has the same advantages as those described inconjunction with transducer 30 of FIGS. 3 and 4. It is understood thatbending member 82 can also be made of other materials such as describedpreviously for the diaphragm transducer and will have certain desirablecharacteristics according to the material chosen.

The above descriptions are made primarily with regard to transducers,but it is understood that the present invention also comprises otherdevices such as actuators.

FIG. 7 is a cross-sectional side view of an acutator 101 utilizing acorrugated diaphragm structure 109 according to the present invention.Diaphragm 109 includes a deflecting member 108 attached to a supportmember 106 via corrugations 110. A substrate 107 having an aperture 111and a substrate well 112 is attached to support member 106. Attached tothe opposite side of support member 106 is a superstrate 103 havingapertures 104 and 105 and a superstrate well 113. Diaphragm 109 can beconstructed from silicon or from other materials such as describedpreviously for the diaphragm transducer and will have certain desirablecharacteristics according to the material chosen.

In operation, application of a control pressure through aperture 111 tosubstrate well 112 causes deflecting member 108 to move. A flow of fluidthrough aperture 104 to superstrate well 113 and back through aperture105 can be controlled by the displacement of deflecting member 108 whichitself is controlled by the control pressure in substrate well 112. Thusactuator 101 can operate, for example, as a valve.

Actuator 101 thus has an advantage over prior art flat diaphragmactuators in that there is a larger vertical travel displacement and agreater linear response range of diaphragm 109 due to corrugations 110.This allows the actuator of the present invention to be more accurate,more sensitive, and much smaller than prior art actuators.

In summary, it has ben shown that the transducers and actuators of thepresent invention have significant advantages over prior art transducersand actuators. Also, the method of manufacture of the present inventionproduces reliable, easy to manufacture, more easily controllable, andless costly transducers and actuators than prior art devices.

Although the present invention has been described in accordance withspecific illustrative embodiments, one of ordinary skill in the art willrecognize that a variety of modifications can be made to theseembodiments and such modifications are within the spirit and scope ofthe present invention. The scope of the present invention is defined,therefore, solely by the scope of the following claims.

What is claimed is:
 1. A method for forming at least one corrugation ina semiconductor material comprising the steps of:(a) masking a firstsurface of said semiconductor material in accordance with apredetermined pattern; (b) etching said first surface in accordance withsaid predetermined pattern to provide a predetermined profile on saidfirst surface; (c) removing said mask from said first surface; (d)providing an etch stop on said surface in accordance with saidpredetermined profile; and (e) etching second surface that is oppositesaid first surface to said etch stop to form said corrugation.
 2. Themethod of claim 1 further comprising the step of providing a mask onsaid second surface after said etch stop is provided to form a supportmember.
 3. The method of claim 1 wherein step (a) comprises oxidizingsaid semiconductor material.
 4. The method of claim 1 wherein step (b)comprises etching said semiconductor material with a plasma etchant. 5.The method of claim 1 wherein step (d) comprises diffusing an etch stopin said material to a depth of between 0.3 μm and 20 μm.
 6. The methodof claim 1 wherein step (d) comprises diffusing an etch stop in saidmaterial to a depth determined by the depth of a diffused semiconductordopant.
 7. The method of claim 1 wherein step (d) comprises thedeposition of a thin film material conforming to said predeterminedprofile, said thin film material being unreactive with said secondsurface etching of step (e).
 8. The method of claim 7 wherein said thinfilm material is selected from the group consisting of sputtered metalfilm, evaporated metal film, plated metal film vapor depositeddielectric film, and polymer coating.
 9. The method of claim 1 whereinstep (d) comprises forming said deflecting member and said corrugationsfrom the group consisting of sputtered metal, evaported metal, platedmetal, vapor deposited dielectric, and polymers.
 10. The method of claim1 wherein step (e) comprises anisotropically etching said oppositesurface.
 11. The method of claim 1 wherein step (e) comprisesisotropically etching said opposite surface.
 12. The method of claim 1in which said etch stop includes etching with a material selected fromthe group consisting of boron, phosphorous, arsenic, antimony oraluminum.
 13. A method for forming from a semiconductor material asemiconductor transducer having a deflecting member supported by atleast one corrugation, comprising the steps of:(a) masking a firstsurface on said semiconductor material in accordance with a firstpredetermined pattern; (b) masking a second surface on saidsemiconductor material in accordance with a second predeterminedpattern; (c) etching said first surface in accordance with saidpredetermined pattern to provide a predetermined profile on said firstsurface; (d) removing said mask from said first surface; (e) providingan etch stop on said first surface in accordance with said predeterminedprofile; and (f) etching the unmasked portion of said second surface toform said corrugaton and said deflecting member.
 14. The method of claim13 further comprising the step of providing a mask on said secondsurface after said etch stop is provided to form a support memberthereon.
 15. The method of claim 13 wherein step (a) comprises oxidizingsaid oxidizing said semiconductor material.
 16. The method of claim 13wherein step (b) comprises etching said semiconductor material with aplasma etchant.
 17. The method of claim 13 in which step (d) comprisesdiffusing an etch stop in said material to a depth of between 0.3 μm and20 μm.
 18. The method of claim 13 wherein step (e) comprises diffusingan etch stop in said material to a depth determined by the depth of adiffused semiconductor dopant.
 19. The method of claim 13 wherein step(e) comprises the deposition of a thin film material conforming to saidpredetermined profile, said thin film material being unreactive withsaid second surface etching of step (f).
 20. The method of claim 19wherein said thin film material is selected from the group consisting ofsputtered metal film, evaporated metal film, plated metal film, vapordeposited dielectric film, and polymer coating.
 21. The method of claim13 wherein said (e) comprises forming said deflecting member and saidcorrugations from the group consisting of sputtered metal, evaporatedmetal, plated metal, vapor deposited dielectric, and polymers.
 22. Themethod of claim 13 in which step (f) comprises anisotropically etchingsaid second surface.
 23. The method of claim 13 wherein step (f)comprises isotropically etching said second surface.
 24. The method ofclaim 13 in which said etch stop includes boron.
 25. A method forforming a semiconductor structure having a deflector member supported byone or more corrugations, comprisng the steps of:(a) etching a firstsurface of a semiconductor material in accordance with one or morepredetermined patterns to provide a predetermined profile on said firstsurface; (b) providing one or more etch stop features on said firstsurface in accordance with said predetermined profile and in accordancewith one or more predetermined patterns; and (c) etching a secondsurface of said semiconductor material in accordance with anotherpredetermined pattern to form said corrugations and said deflectingmember.